In general, a dynamometer is arranged to sense a repulsion torque acting between a rotor and a swing frame, with a load measuring device (such as load cell) through a torque arm provided in the swing frame, and to measure its driving, absorbing power. The dynamometer is provided with a torque calibration apparatus to perform periodical inspection and correction as to whether the measuring accuracy is invariably maintained.
As shown in FIG. 8(a), a torque calibrating apparatus of a patent document 1 includes a weight shaft 2 connected with a calibration arm is of a dynamometer 1, a weight placement section 3 supported by the weight shaft 2, and a load measuring device 5 disposed between a torque arm 1b and a fixing portion 6. Weights 4 are stacked or piled one by one on the weight placement section 3, and the torque is calibrated from the output of load measuring device 5.
The load of weights stacked one by one on the weight placement section 3 is compared with the indicated load of load measuring device 5, and the torque calibration is performed by checking whether the indicated load of the load measuring device 5 is within an allowable range.
Each of the weights 4 is in the form of a flat plate having a substantially rectangular shape, and formed with a cutout portion 9 between sides 4a and 4c forming the longer sides of the rectangular shape, as shown in FIG. 8(b). The cutout portion 9 extends from the middle of the side 4a toward the opposite side 4c. Each weight 4 is stacked on the weight placement section 3 in the state in which the weight shaft 2 is inserted into the cutout portion 9.